Ionization tube structure



March 13, 1934. A. HUND IONIZATION TUBE STRUCTURE Filed Dec. 15, 1932 ELIE-E (Z Wurk anode pnie INVENTOR August Hmui ATTORNEY Patented Mar. 13, 1934 IONIZATION TUBE STRUCTURE August Hund, West Orange, N. J., assignor to Wired Radio, Inc., New York, N. Y., a corporation of Delaware Application December 15, 1932, Serial No. 647,341

4 Claims.

This invention relates to gaseous discharge tubes and has particular reference to the structural details thereof and to the adaptation of such tubes for a wide range of uses in electrical circuits generally.

An object of my invention is to provide a discharge tube of this character comprising a plurality of electrodes with insulated leads therefor, suitable to the peculiar manner of activating such tubes.

Another object of my invention is to provide means in combination with the leads and sup ports for the electrodes of these tubes for preventing the creepage of glow discharge along the outer insulation walls of the leads and supports.

Another object of my invention is to so proportion and shape the respective activated areas of the electrodes and to envelope the same in a suitable gas at a suitably attenuated pressure so that optimum conditions may be obtained for the operation of such tubes.

Another object of my invention is to provide a glow discharge tube of the class described in which the structure and arrangement of the elec trodes themselves is best adapted for exhibiting a high degree of power gain between the input and output circuits of the tube, and a minimum wattage consumption in the ionizing circuit as well as in the work circuit.

This application is a continuation in part of my application, Serial No. 624,928, filed July 2'7, 1932. In that application I have shown a gaseous discharge tube having an electrode structure somewhat similar towhat is herein shown. In this application, however, I have developed a su-' perior structure by the use of which improved results are obtained and a tube is provided, the efficiency of which endures for a longer life.

With the aforementioned objects in view the novel construction of my gaseous discharge tube will be more fully understood from the following description and by reference to the accompanying drawing in which:

Fig. 1 depicts an elevation of one embodiment of a gaseous discharge tube having its ionizing electrodes disposed externally of the work electrode system;

Fig.2 shows a modification of the electrode structure in which the ionizing electrodes are 0 again external to the work electrodes;

Fig. 3 is an alternate embodiment of the gaseous discharge tubes of my invention showing the ionizing electrodes disposed internally of the work electrode system;

Fig. 4 shows a slight modification of the electrode structure when compared with the tube of Fig. 3; and

Fig. 5 is a curve diagram showing the operating characteristic of gaseous discharge tubes as herein disclosed in comparison with the characteristic of tubes such as are shown and described in my aforementioned copending application, Serial No. 624,920.

I have discovered that in operating gaseous discharge tubes such as shown and described in some of my previously filed copending applications including Serial No. 624,920 aforementioned, that there is a tendency for the ionizing electrodes to sputter and deposit a metallic film upon the outer walls of the leads and electrode supports. The glow discharge is attracted to this film deposit and gradually creeps along the outer walls of the insulated electrode leads thereby destroying the eiliciency of operation of the tube. In order to overcome this diificulty I have made use of a skirtlike structure surrounding the leads at their electrode extremities. The tendency to sputter is then confined within the skirts. The limitation imposed by the dimensions of the skirts themselves renders such sputtering and metallic deposits relatively harmless to the proper operation of the tube. When once a metallic film deposit is made within these skirts the tendency to creepage of the glow discharge is definitely and permanently arrested.

As a still further improvement of my gaseous discharge tubes for the purpose of lengthening their life, I have found that it isadvantageous to localize the primary glow discharge as far as possible in regions near the ionizing electrodes facing toward the work electrodes. It is evident that a glow discharge extending from the ionizing electrodes in a direction opposite to that of the work electrodes can have little, if any, utility in projecting streams of controllable ions and electrons. Furthermore, such ionization away from the work electrodes is not only wasteful of electrical energy, but it tends to increase the rate at which conductive coatings are sputtered upon the glass within the tube. The avoidance of this diiliculty by structural design of the elements themselves will be hereinafter explained.

I have found that the tendency of the glow discharge to cause conductive coatings by sputtering is somewhat dependent upon the material of which the electrodes are composed. Thus, aluminum has a very low sputtering factor, but, due to its low melting point and its low mechanical strength, it is less desirable for use in making the electrodes than svea, a metal made from the purest Swedish iron base. Nickel causes sputtering more than svea but it is mechanically better than svea in many of the tube designs which I prefer, because svea is so soft that it does not keep its shape readily. From the standpoint of rugged construction, nickel is a satisfactory electrode material and its sputtering factor is not a serious obstacle to its use when other means are provided for limiting the sputtering effects. I am in no way limiting myself to the use of nickel, however.

Referring now to Fig. 1, a gaseous discharge tube is shown having a suitable envelope 1 and base 2 of well-known type. The several electrodes of the tube are connected by leads 3 with the prongs 4. The leads are suitably insulated as by the glass tubes 5. At the electrode extremities of the leads or supporting posts, or any of them, skirt members 6 of insulating material may be provided. It is particularly desirable that the leads to the ionizing electrodes be so equipped.

In the embodiment of my invention as shown in Fig. 1, there is an ionizing cathode '7, preferably of an open-ended cylindrical formation. Spaced slightly away from the cathode I provide one or two ionizing anodes 8. These may be in the form of simple wire rings and are preferably of slightly smaller diameter than that of the cylindrical cathode. Better eiriciency and less sputtering are obtained by this difference of diameter since the glow discharge is practically confined within the inner walls of the cathode.

Axially disposed within the ionizing electrodes I provide a control electrode 9 which may consist of a helical formed wire supported by a straight post 10. At the very center of the electrode structure I provide a work anode 11 which may be in the form of a straight piece of wire.

While there are some advantages in having two ionizing anode rings, I find that tubes of this character will function satisfactorily when only one such ionizing anode ring is provided. In most cases the working area of the ionizing cathode is greater than that of the ionizing anode. This area relationship provides the advantage that an excess of negatively charged ions and electrons is available at the ionizing cathode '7 for building up a space current toward the work anode 11. This space current may then be suitably modulated as it passes through the mesh of the control electrode 9 when variations of potential are applied to the latter.

Referring to Fig. 2, I show a modification of gaseous discharge tube structure in which the ionizing cathode 7a is in the form of a simple wire ring and the ionizing anode 8a is in the form of a crimped wire ring. One or more points of support may be provided for these electrodes and whether or not they are electrically connected to their leads at more than one point for each electrode will be understood to be a matter of practical expediency. Thus, while I have shown the cathode 7a as supported at two points with electrical conductors at both of these points, it is not essential that more than one electrical conductor should be so provided, even if there are two points of support. It is, however, preferable that the skirt members 6 be provided at the points of support of the ionizing electrodes in all cases and it may also be found desirable in some cases to use these skirt members about the leads and supports for the other electrodes. Without further description, the tube structure in Fig. 2 will be seen go be similar in many respects to that shown in Referring now to Figs. 3 and 4, I show certain modified electrode structures in which the ionizing electrodes are disposed internally of the work electrodes. As shown in Fig. 3, the ionizing cathode 12 may be in the form of a hollow cylinder, the walls of which are perforated with small holes to permit of the projection of negatively charged ions and electrons outwardly toward the work anode 13. The primary glow discharge is substantially confined within the walls of the cylindrical cathode 12 by reason of the location of the ionizing anode 14 axially with respect to the cathode. Such an ionizing anode, while not easily discernible in Fig. 3, will be understood to be in the form of a simple straight piece of wire, or a solid cylinder, supported by the post 14. A similar ionizing anode 15 is shown in Fig. 4 where it is axially disposed with respect to the helically formed ionizing cathode 12a.

In Fig. 4 as well as in Fig. 3, the control electrode 9 is seen to be of helical formation surrounding the ionizing electrodes and disposed between them and the work anode 13. This work anode is preferably in the form of a crimped cylindrical band. The skirt members 6 are shown in Figs. 3 and 4 suitably disposed for the prevention of creepage of glow discharge away from the useful regions therefor. It will be seen from a comparison of the ionizing cathode structures in Figs. 3 and 4 that the openings provided by the perforations of the cylinder 12 and the open construction of the helix 12a provide equivalent facilities for the projection of negatively charged ions and electrons outwardly toward the work anode 13. rents set up in the output circuits of such tubes between the work anode and the ionizing anode may be suitably controlled by variations in the potential of the control electrode so as to provide amplification. The open mesh construction of the control electrode renders such functioning of the tube possible in a manner which is well understood.

While in Figs. 3 and 4 the ionizing cathode is shown surrounding the ionizing anode, I have, nevertheless, successfully operated these tubes with the polarities of the ionizing electrodes reversed. Upon such reversal, it is necessary to provide other potentials for the work anode and the control bias respectively.

Referring now to Fig. 5, a comparison of the operating characteristic of my improved gaseous discharge tube with that of tubes such as shown in my copending application, Serial No. 264,290. may readily be seen. In the improved tubes of the instant disclosure an almost complete control of the work anode current is obtained.

The relation between the work anode current and the work anode potential exhibited by my improved tubes (as illustrated in Figs. 3 and 4) is shown by the full line curve drawn through the points O-abe. The characteristic of my earlier type of tubes having internal ionization electrodes is shown, for comparison, by the broken line curve through the points Ocdf. For most applications, the useful portions of the curves are from b to e in the case of the improved type, and from d to ,f for the older type of tube. The portions of the curves from O to a and from O to 0 respectively, represent conditions under which the power is insufficient to set up a secondary glow in the region between the work anode and a space close to the control electrode. For this reason, if the tube is to be used as an amplifier or demodulator, the operating point would not be set to include these portions of the curves.

It will be further understood that the cur- The portions of the curves beyond 6 and 7, respectively, would have utility only in special applications not now under consideration, since the high potentials cause a streamer discharge between the work anode and the control electrode, as explained in detail in my copending application, Serial No. 264,920.

A comparison of the full line curve with the broken line curve shows clearly the greatly increased range through which the work anode current of my improved type of tubes may be con trolled; that is, from b to e. The minimum point I) is very close to zero value. For the older type of tubes the useful control of work anode current was limited to the range of values between dud and fof.

In orer that my experiments which have produced the desirable results, as hereinbefore set forth, may be repeated by any one skilled in the art, I may say that a certain tube of the class shown in Fig. 3 was further characterized as follows: The crimped work-anode was made of a ribbon 6 mm. in width and 24 mm. inside diameter. The diameter of the control electrode was 12 mm. and the helix was composed of 12 turns having a total axial length of 20 mm. The ionizing cathode had a diameter of 4 mm. and was 6 mm. long. The work anode current could be controlled from 60 milliamperes down to about 0.25 milliamperes.

Detailed specifications with respect to another illustrative tube of my invention which was made more according to Fig. 1, although having only one anode ring instead of two as shown, are as follows:

The ionization cathode cylinder was of 15 mm. inside diameter and had an axial length of 7 mm. The positive ionization ring was disposed 2 mm. below the lower edge of the cathode. Its outside diameter was about the size of the inside diame ter of the cathode. The control electrode consisted of a helix having sixteen turns wound so as to be '7 mm. in diameter and 25 mm. in length. The work anode was disposed axially and was 16 mm. in length. The electrode structure was enveloped in an atmosphere of helium gas at 40 mm. mercury pressure. Another tube of similar structure had an atmosphere of nitrogen at 10 mm. mercury pressure. The work anode current of this tube had a mean value of 4 milliamperes. Its ionization current was 11 milliamperes when the primary glow discharge extended completely around the inner face of the ionization cathode cylinder. Had the design been such that the ionization anode ring exceeded in diameter that of the cathode, then the glow discharge would have been both outside and inside the cathode cylinder and the ionization current would have been at least twice as great.

Conservation of power for maintaining the glow discharge is, therefore, attributable in part to the relative dimensions of the electrodes. Furthermore, the dimensions of the skirt members 6 can be adjusted so as to contribute toward ellicient operation. It will, nevertheless, be manifest that no restrictions are imposed upon the carrying out of my invention by adherence to any particular dimensions of the elements in combination. The scope of the invention is limited only in accordance with the claims themselves.

I claim:

1. In a gaseous discharge tube, a work anode, a control electrode, an ionizing cathode, an ionizing anode of orimped formation such as to present a plurality of apexes toward the working area of said cathode, leads for said electrodes, insulation of glass or the like about said leads, and means including skirts of insulating material at the electrode extremities of said leads whereby metallic deposits, such as caused by sputtering upon the insulation of said leads, is prevented.

2. In a gaseous discharge tube, a work anode of corrugated metal ribbon formed into a ring, a helical shaped control electrode concentrically and internally disposed with respect to said work anode, an ionizing cathode of orificed or meshed cylindrical formation concentrically and internally disposed with respect to said control electrode and an ionizing anode axially disposed within said ionizing cathode, said electrodes being further characterized in that a primary glow discharge may be set up and substantially confined within said cathode while negative ions are ejected from the region of primary glow discharge through the mesh of said control electrode and toward said work anode.

3. A gaseous discharge tube as defined in claim 2 further characterized in that insulated leads are provided for said electrodes and skirts of insulating material are disposed about said leads at the electrode extremities thereof for preventing the creepage of glow discharge along the insulation of said leads.

4. In a gaseous discharge tube, a work anode, a control anode, an ionizing cathode, an ionizing anode formed to present a plurality of apexes toward the activated area of said cathode, leads for said electrodes, insulation about said leads, and means including skirts of insulating material at the electrode extremities of the leads for said ionizing electrodes for preventin the creeping of the glow discharge between said electrodes along the insulation on said leads.

AUGUST HUND. 

